Propeller



W. W. SMITH.

PROPELLER.

APPLICATION FILED MAR. 22, I920- Patented June 7, 1921.

. kind of fluid such as air or water.

we STATES FATE WILLIAM W. SMITH, 9F BUFFALO, YORK, ASSIGNOR 0F ONE-HALF T0 WILLIAM G. BIDDER, 0F BUFFALO, NEW YORK. I

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Specification of Letters Patent.

Patented time '7, 1921..

To all whom it may concern:

Be it known that 1', WILLIAM W. SMITH,

a citizen of the United States, residing in Buffalo, in the county of Erie and'State of New York, have invented new and useful Improvements in Propellers, of which the following is a specification.

This ipvention relates to a driving propeller or rotatable screw for propelling air craft or water craft, and relates more particularly to a reinforced all-metal propeller for aeroplanes.

One of the objects of the invention is to provide a light and yet strong propeller which is weatherproof and waterproof and cannot be warped br bent out of shape, whereby the propeller blades are enabled to preclsely retain their original balance and pitch. to provide the propeller blades with suitable bracing or stiffening webs for taking up the stresses due to the thrust and twisting of the propeller. A still further object of the invention is to provide light hollow propeller blades of streamline form wherelo the desired thrust of the propeller is obtained with a minimum of circumferential air resistance. Further objectsand advantages will appear more clearly in the following specification and accompanying drawings wherein Figure 1 is an end view of the improved reinforced propeller. Fig. 2 is a transverse section through the blades of the propeller taken on line 2-2, Fig. 5. Figs. 3 and 4: are transverse sections through one of the propeller blades taken on correspondingly numbered lines of Fig. 1. Fig. 5 is a section taken through the hub of the propeller in a plane parallel with the axis of the propeller on line 55, Fig. 2.

Similar characters of reference refer to:

like parts throughout the several views.

This invention is applicable to the screw propulsion of either water and air craft and may also be associated with rotary or handle any The drawings, however, only disclose the invention as applied to an aeroplane propeller, the same being shown in end elevation in Fig. 1. The numeral 10 represents the hub or central thickened part of the propeller, saidhub being provided with a central longltudinal hole 11 which is adap d to receive a pro? force pumps or blowers which A further object of the invention is peller shaft, not shown, upon which the propeller is adapted to rotate. The hub 10 is further provided with a suitable key way 12, whereby the propeller is constrained to rotate with the propeller shaft. The longitudinal central part of the hub is suitably hollowed or cored out at 13 for the purpose of lightening the propeller without how; ever, decreasing the overall length of the hole'll'. It is obvious that if the overall length of the hole 11 were short, the propeller would tend to become loosened or to rock onthe propeller shaft after considerable usage, whereas by hollowing the hiib at 13, the said hub is not only rendered lighter but the only metal which is removed is that which has no appreciable effect in preventing the propeller from rocking on thepropeller shaft. The hub of the propeller may also be provided with a circumferential row of longitudinal bolt holes 14, which are adapted, in a manner common in the aeronautic art, to receive suitable bolts which pass into a suitable flange on the propeller shaft.

Connected preferably integrally with said hub 10 are two or more hollow propeller blades, each of which comprises an inclined rear thrust face 15 and a front blade face 16, the former being the driving face which compresses the air layers immediately adj acent thereto, as the propeller is caused to revolve, thereby creating the thrust of the propeller. The front blade face 16 is, of

course, caused, when the propeller is rotated,

to float in a partial vacuum area, and therefore the shape of said front face 16 is arranged to be of streamline form so as to revent undue eddy air currents from curling around the cutting edge 18 of the blade and thereby impairing the efiiciency of the. low pressure area, the action being similar to the action of the air currents on the main wings of an aeroplane. The outer ends and the adjacent edges of the companion faces 15 and 16 of each blade are preferably connected integrally together so as to present a smooth unbroken surface around the entire perimeter of the blade, thereby excluding all moisture from the hollow ortion of the blade and also providing or a minimum of skin and head-on air resistance of said blade.

Arranged longitudinally within the h0llow part of each propeller blade is a bracing or stifiening rib 20, whose opposite edges are preferably integrally secured to the opposite faces and 16 of said blade and whose opposite ends are secured respec-- tively to the hub 10 and the outer ti 19 of said blade. The plane of this stiffening rib 20 is parallel to the axis of the propeller, that is of the hole 11, so that the strains which are set up by reason of the thrust of the propeller are carried by this stiffening rib, whose plane therefor is parallel to the strain imposed upon it. Projectin outwardly from each longitudinal sti enin rib 20 is a laterally extending rib 21 whic is preferably integrally secured on its opposite edges to the opposite faces 15 and 16 'of each propeller blade and whose opposite-ends are preferably integrally secured respectively, as the case may be, either to therib 20 and the front or the rear edge of .the propeller blade. The plane of these laterally extending ribs 21 is, similarly to the ribs 20, 'i. 0., parallel to the axis of the propeller. Each of these lateral ribs 21 however, is arranged-at an angle relatively to its companion longitudinal rib 20. The angle may be any desired number of de rees up to 180 degrees, but in the preferre arrangement shown in the drawings, these lateral ribs extend outwardly from their companion longitudinal ribs 20 in a manner similar to that in which the finer stiffening veins extend like a fan out from the stem of face of the blade.

a plant leaf. These laterally extending ribs 21 serve to sustain those twisting strains of the propeller blade which tend to alter the pitch or angle of said blade.

These twisting strains are caused by unequalized pressures at different parts of the faces of the blades, resulting from a number of causes which need not be here discussed except to state in a general way-that the principal air pressure is exerted just behind the leading edge 18 of each propeller blade and not the eometrical center of the ere the entire propeller is cast in one piece, it is of course, necessary to remove the-core sand from the hollow pockets of each blade and for this purpose suitable holes 23 are formed in the appropriate parts of the blade walls and are suitably plugged up by means of plugs 24 after the said core sand has been removed. It is obvious however, that these plugs 24 may be I dispensed with, where the propeller is cast propeller is rendered very light without weakening the strength of the same or allowing the propeller to get loose on its shaft. Furthermore, the propeller can be constructed entirely by machinery with an automatically accurate precision that is not possible with an ordinary laminated wood propeller which requires very skilled manual labor for all operations except the roughing cuts. Furthermore, inasmuch as this improved propeller may be constructed of metal which does not vary appreciably in specific gravity, the propeller as it comes from the final finishing machines needs but little to balance it accurately, whereas the forms of wooden propellers have to be altered considerably to obtain the all vital balance of the propeller.

The whole propeller can be cast in one piece with various numbers of blades and is preferably made from a special formula of alloyed metals, the greater portion being pure aluminum, the other metals of the alloy being added to Ii hten and strengthen and bring it to a suitable degree of hardness for smooth finish and to secure a tensile strength of over 18,000 pounds.

I claim as my invention:

1. A propeller having hollow blades reinforced by longitudinal stiifening ribs, and

lateral stifi'ening ribs extending outwardly ing out from both sides of said longitudinal ribs and at an oblique angle relatively thereto.

WILLIAM W. SMITH. 

